Windows Vista RC1 is signed off and done - it will be available "real soon now". Same for the Windows SDK (which contains the Mobile PC/Tablet PC bits).
I signed on to connect.microsoft.com and wasn't able to find either one though.
You should be able to download these very soon and the build number is 5600. We've come a long way since Beta2 and the intervening refreshes.
Enjoy and please send me your Tablet-specific issues! There are other channels for your non-Tablet issues :p (hint: http://forums.microsoft.com/msdn )